/*
 * Copyright (C) 2011 The Guava Authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
 * in compliance with the License. You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software distributed under the License
 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
 * or implied. See the License for the specific language governing permissions and limitations under
 * the License.
 */
package com.google.common.collect;

import com.google.common.annotations.GwtCompatible;
import com.google.common.annotations.GwtIncompatible;

import java.io.Serializable;
import java.util.NoSuchElementException;
import java.util.Set;
import javax.annotation.CheckForNull;

/**
 * An empty contiguous set.
 *
 * @author Gregory Kick
 */
@GwtCompatible(emulated = true)
@SuppressWarnings("rawtypes") // allow ungenerified Comparable types
@ElementTypesAreNonnullByDefault
final class EmptyContiguousSet<C extends Comparable> extends ContiguousSet<C>
{
    EmptyContiguousSet(DiscreteDomain<C> domain)
    {
        super(domain);
    }

    @Override
    public C first()
    {
        throw new NoSuchElementException();
    }

    @Override
    public C last()
    {
        throw new NoSuchElementException();
    }

    @Override
    public int size()
    {
        return 0;
    }

    @Override
    public ContiguousSet<C> intersection(ContiguousSet<C> other)
    {
        return this;
    }

    @Override
    public Range<C> range()
    {
        throw new NoSuchElementException();
    }

    @Override
    public Range<C> range(BoundType lowerBoundType, BoundType upperBoundType)
    {
        throw new NoSuchElementException();
    }

    @Override
    ContiguousSet<C> headSetImpl(C toElement, boolean inclusive)
    {
        return this;
    }

    @Override
    ContiguousSet<C> subSetImpl(
            C fromElement, boolean fromInclusive, C toElement, boolean toInclusive)
    {
        return this;
    }

    @Override
    ContiguousSet<C> tailSetImpl(C fromElement, boolean fromInclusive)
    {
        return this;
    }

    @Override
    public boolean contains(@CheckForNull Object object)
    {
        return false;
    }

    @GwtIncompatible // not used by GWT emulation
    @Override
    int indexOf(@CheckForNull Object target)
    {
        return -1;
    }

    @Override
    public UnmodifiableIterator<C> iterator()
    {
        return Iterators.emptyIterator();
    }

    @GwtIncompatible // NavigableSet
    @Override
    public UnmodifiableIterator<C> descendingIterator()
    {
        return Iterators.emptyIterator();
    }

    @Override
    boolean isPartialView()
    {
        return false;
    }

    @Override
    public boolean isEmpty()
    {
        return true;
    }

    @Override
    public ImmutableList<C> asList()
    {
        return ImmutableList.of();
    }

    @Override
    public String toString()
    {
        return "[]";
    }

    @Override
    public boolean equals(@CheckForNull Object object)
    {
        if (object instanceof Set)
        {
            Set<?> that = (Set<?>) object;
            return that.isEmpty();
        }
        return false;
    }

    @GwtIncompatible // not used in GWT
    @Override
    boolean isHashCodeFast()
    {
        return true;
    }

    @Override
    public int hashCode()
    {
        return 0;
    }

    @GwtIncompatible // serialization
    private static final class SerializedForm<C extends Comparable> implements Serializable
    {
        private final DiscreteDomain<C> domain;

        private SerializedForm(DiscreteDomain<C> domain)
        {
            this.domain = domain;
        }

        private Object readResolve()
        {
            return new EmptyContiguousSet<>(domain);
        }

        private static final long serialVersionUID = 0;
    }

    @GwtIncompatible // serialization
    @Override
    Object writeReplace()
    {
        return new SerializedForm<>(domain);
    }

    @GwtIncompatible // NavigableSet
    @Override
    ImmutableSortedSet<C> createDescendingSet()
    {
        return ImmutableSortedSet.emptySet(Ordering.natural().reverse());
    }
}
